Shao tian

03-09-2011, 02:29 PM

Hey guys:

I am trying to shade opengl point sprites to make them look like spheres. The shading model I am using is (color = emissive + ambient + diffuse + specular). Could any one help to see what kind of mistake might cause this problem. To see what problem is, please have a look at attached screenshot. They supposed to look like spheres with lighting effect. But the current resulting effect looks so strange.

I also attach the CG fragment program code here.

vec4 mesh_fragment(uniform float4 c:COLOR,

float2 texCoord:TEXCOORD0,

uniform sampler2D decal):COLOR

{

float4 position=float4(texCoord,0,1);

float2 normal;

normal= texCoord.xy* 2.0 - vec2(1.0);

float mag = dot(normal.xy, normal.xy);

if (mag > 1.0) discard; //clip the point sprite to make it a circle

//start initializing shading model parameters

float3 Ke={0,0,0};

float3 Ka={0,0,0};

float3 Ks={1, 1, 1};

float3 Kd={1, 1, 1};

float3 globalAmbient={1,1,1};

float3 lightColor={1,1,1};

vec3 lightPosition=vec3(-100,100,-100);

float3 eyePosition={0, 0, 13};

float shininess=32.0;

//Start performing shading model algorithm

float3 P = position.xyz;

float3 N = float3(normalize(normal),0);

// Compute emissive term

float3 emissive = Ke;

// Compute ambient term

float3 ambient = Ka * globalAmbient;

// Compute the diffuse term

float3 L = normalize(lightPosition - P);

float diffuseLight = max(dot(N,L), 0);

float3 diffuse = Kd * lightColor * diffuseLight;

// Compute the specular term

float3 V = normalize(eyePosition - P);

float3 H = normalize(L + V);

float specularLight = pow(max(dot(N,H), 0), shininess);

if (diffuseLight <= 0) specularLight = 0;

float3 specular = Ks * lightColor * specularLight;

float4 color;

color.xyz = emissive + ambient + diffuse + specular;

color.w = 1;

return color;

}

I am trying to shade opengl point sprites to make them look like spheres. The shading model I am using is (color = emissive + ambient + diffuse + specular). Could any one help to see what kind of mistake might cause this problem. To see what problem is, please have a look at attached screenshot. They supposed to look like spheres with lighting effect. But the current resulting effect looks so strange.

I also attach the CG fragment program code here.

vec4 mesh_fragment(uniform float4 c:COLOR,

float2 texCoord:TEXCOORD0,

uniform sampler2D decal):COLOR

{

float4 position=float4(texCoord,0,1);

float2 normal;

normal= texCoord.xy* 2.0 - vec2(1.0);

float mag = dot(normal.xy, normal.xy);

if (mag > 1.0) discard; //clip the point sprite to make it a circle

//start initializing shading model parameters

float3 Ke={0,0,0};

float3 Ka={0,0,0};

float3 Ks={1, 1, 1};

float3 Kd={1, 1, 1};

float3 globalAmbient={1,1,1};

float3 lightColor={1,1,1};

vec3 lightPosition=vec3(-100,100,-100);

float3 eyePosition={0, 0, 13};

float shininess=32.0;

//Start performing shading model algorithm

float3 P = position.xyz;

float3 N = float3(normalize(normal),0);

// Compute emissive term

float3 emissive = Ke;

// Compute ambient term

float3 ambient = Ka * globalAmbient;

// Compute the diffuse term

float3 L = normalize(lightPosition - P);

float diffuseLight = max(dot(N,L), 0);

float3 diffuse = Kd * lightColor * diffuseLight;

// Compute the specular term

float3 V = normalize(eyePosition - P);

float3 H = normalize(L + V);

float specularLight = pow(max(dot(N,H), 0), shininess);

if (diffuseLight <= 0) specularLight = 0;

float3 specular = Ks * lightColor * specularLight;

float4 color;

color.xyz = emissive + ambient + diffuse + specular;

color.w = 1;

return color;

}